I've read that wetlands and other ecosystems clean the environment of potentially harmful human-created chemicals. Just how do plants do this. Are the chemicals merely taken out of the soil and water temporarily while the plants hold them? If the plants render the chemicals harmless, how do the plants alter the toxic molecules?Thanks,Matt

In the environment, there are plants and microorganism that can take up chemical that are potentially harmful to human. Using them in their biochemistry pathway and the end product become something harmless to human, so they are not holding or keeping them, but this is a cycle. For instance, some bacteria able to degrade pollutant.

for example, plants can be used for remediation of heavy metals. In such cases, they take it up with other ions in water and store them bound to proteins containing lot of sulfhydryl groups. After growing they are burned and the metals taken from the ash.